Perennials, 10-30 cm (with crown buds). Stems (green or purplish) erect, glabrous. Leaves mostly basal; opposite; petioles 0-1 cm; blades linear to narrowly obovate, 13-30 × 0.7-2 cm, bases cuneate, margins entire or obscurely serrate, faces glabrous, not gland-dotted (cauline smaller). Heads 3-12. Peduncles 4-11 cm. Involucres hemispheric, 8-12 mm diam. Phyllaries 18-23, linear-linear, 5-11 × 1-2.5 mm, (margins ciliolate) apices ± attenuate, abaxial faces glabrate or glabrous. Paleae 6-8 mm, weakly 3-toothed (apices hairy). Ray florets 8-13; laminae 10-19 mm (abaxial faces not gland-dotted). Disc florets 35+; corollas 4.2-5.5 mm, lobes yellow; anthers dark, appendages dark. Cypselae 2-3 mm, glabrate; pappi of 2 aristate scales 1.4-2.5 mm. 2n = 34. Flowering late summer-fall. Sandstone and granite outcrop edges; 100-600 m; Ala., Ga., N.C. Helianthus longifolius is locally escaped from a planting in one county in North Carolina. It is locally abundant where it occurs. It is not similar to or closely related to any other species; natural hybrids of H. longifolius with H. atrorubens and H. occidentalis are known.